'Watching the World Change': Images of Sept. 11On Sept. 11, 2001, thousands of ordinary citizens joined some of the world's best photojournalists at the World Trade Center towers to chronicle the horror and bravery of that day.

Audio Commentary by David Friend: 'Over Time, People Will Persevere.'

On Sept. 11, 2001, thousands of ordinary citizens joined some of the world's best photojournalists in chronicling the horror of that day. Watching the World Change by David Friend is a new book that tells some of the stories behind those gripping photographs, centering on the attack on the World Trade Center in lower Manhattan.

Like most Americans, Friend, an editor at Vanity Fair magazine, says he remembers the day very clearly. He was crossing Times Square on his way to his office and looked up just in time to see one of the towers collapsing on the jumbo TV screen that is a Times Square landmark.

A former photojournalist, Friend had been looking for one project to examine in depth for a while — and his quest and history collided.

"I'd always had this concept that you could take the DNA of history, or a slice of time, through its pictures," he says. "Looking at the events of [Sept. 11] and its aftermath, I thought 'You know, we really learned about it and processed it and grieved through photographs."

There were photos of the towers' smoking ruins, of course, people fleeing the tsunami of debris after the towers fell, dazed survivors covered in dust and exhausted emergency personnel. But some of the photos that were hardest to look at from that day involve people who fell to their deaths from the towers.

There are many photos of those so-called jumpers — but a single photograph became an icon for the unspeakable choice facing people in the burning towers. In it, an unidentified man plummets head-first to the ground in what appears to be a peaceful pose.

Whether he fell peacefully will never be known — what is without argument is the emotional force of the picture itself. Still, few American newspapers chose to publish the photo, or buried it on the inside pages of coverage of that day.

"Pictures of that sort of power tend to be foreign images," Friend says. "[Americans] don't tend to want to see our own dying before our eyes."

Thanks to the advance of technology, Friend says, photo editors might be faced with even harder choices if a similar event happened today. Mobile phones with digital cameras would be able to send images in real time, from inside the emergency — as happened last summer, when people caught underground during the London transit bombings sent photos from their cell phones.

With the fifth anniversary of the Sept. 11 attacks just days away, many of that morning's most haunting images are likely to haunt Americans yet again.

Friend says that even though the messages are disturbing, there's a reason we can't turn away. "Pictures matter in our lives," he says. "Pictures really are among the only reliable vessels of our understanding of that day."